The invention relates to improving plant efficiency in a combined cycle gas turbine power plant and, more particularly, to a combined cycle power plant including an absorption heat transformer.
In a typical combined cycle system, a gas turbine combusts a fuel/air mixture which expands to turn the turbine and drive a generator for the production of electricity. The hot gases of combustion exhaust into a heat recovery steam generator in which water is converted to steam in the manner of a boiler. Steam thus produced drives a steam turbine, typically comprising high, intermediate and low pressure turbines, in which additional work is extracted to drive a further load such as a second generator for producing additional electric power. In some configurations, the gas and steam turbines drive a common generator and, in others, drive different generators.
In a combined cycle gas turbine power plant, the energy is not sufficiently utilized in the low pressure economizer section, where the exhaust section of flue gas has a lower temperature. It would be desirable to use the lower grade energy to increase plant efficiency.
Absorption heat transformers (AHT) are devices which transform a large heat resource, which is available at temperature too low for correct thermal matching within an industrial process, in a smaller amount of heat available at a higher temperature level. They differ from traditional heat pumps in that they use no (or a very limited amount of) electrical power or work. Basically, AHTs work on the principle of an absorption inverse cycle: however the net effect is that of transferring an amount of heat (smaller than the originally available) at a higher temperature level. This allows recovering this heat into industrial processes.